Dihydropyranyl polyesters



United States Patent 3,480,650 DIHYDROPYRANYL POLYESTERS Josef Sikora, St. Hilaire, Quebec, Canada, assignor to Canadian Industries Limited, Montreal, Quebec, Canada, a corporation of Canada No Drawing. Filed May 31, 1966, Ser. No. 553,665 Claims priority, applicatiorsl G/rgat Britain, July 6, 1965,

5 Int. Cl. cois 17/14, 53/08 US. Cl. 260-3453 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates to dihydropyranyl polyesters and to a process for preparing the same.

In British Patent No. 991,970 to W. D. S. Bowering, N. B. Graham and J. D. Murdock there are described foamable compositions of a novel type comprising a vinyl ether containing at least two vinyl groups per molecule, a foaming agent and an acidic catalyst. Optionally said foamable compositions may contain a compound reactive with said vinyl ether such as a phenol, an alcohol, an epoxidized material, a polycarboxylic acid, a polyamide or a polycarbamate. By variation of the vinyl ether-reactive compound, it is possible to modify the reactivity and fluidity of the compositions to suit desired operating conditions. However, the vinyl ether-reactive ingredients, being structurally different from the vinyl ether ingredient, alter the nature of the foaming reaction. In addition, the need to employ extra ingredients in the foaming compositions requires a more complex foam preparation procedure.

It has now been found that polyester derivatives of cyclic vinyl ethers can be prepared in which the structure of the molecule can be varied so as to modify the properties of foamed cellular polymeric materials employing said polyesters as ingredients. Said polyester compounds comprise an ester intermediate segment constituted by the reaction product of an aliphatic polyhydric alcohol and a lower alkyl ester of an aromatic polycarboxylic acid, said intermediate segment being terminated by cyclic vinyl ether rings. By variation of the structure of the intermediate segment the reactivity and physical properties of the vinyl ether compound can be modified. In this manner the properties of the foaming compositions can be tailored to the desired type of operation and type of foam.

It is thus an object of this invention to provide novel cyclic vinyl ethers useful as ingredients in foamable compositions. A further object is to provide cyclic vinyl ethers whose structures can be designed to suit particular applications of said ethers. Additional objects will appear hereinafter.

The novel cyclic vinyl ether polyesters of this invention comprise compounds having the generic formulas and 3,480,650 Patented Nov. 25, 1969 where n, and 11 are integers having values of at least 2, R is a lower aliphatic radical, Aromatic is a divalent aromatic radical, Aliphatic is a divalent aliphatic radical, A is a linking aliphatic radical having a valence equal to n, and Ar is a linking aromatic radical having a valence equal to n The novel cyclic vinyl ether polyesters of this invention are prepared by means of esterification reactions between an aliphatic polyhydric alcohol, a lower alkyl ester of an aromatic polycarboxylic acid and a cyclic vinyl ether carrying a hydroxyl or carboxylic ester functional group.

In the preferred process for the preparation of the cyclic vinyl ether polyesters of this invention dihydropyranyl methanol and dimethyl phthalate are reacted with an aliphatic polyhydric alcohol in a single step employing an ester exchange catalyst. The by-product methanol is separated from the polyester product by distillation.

In an alternative but less preferred process, the reaction is carried out in two steps. In the first step, a vinyl ether constituted by two dihydropyranyl rings linked by a single ester linkage is reacted with dimethyl phthalate in an ester-ester interchange reaction to produce the methyl ester of dihydropyranyl carboxylic acid and a mixed estermethyl, dihydropyranyl methyl phthalate. The methyl ester of dihydropyranyl carboxylic acid is separated by distillation and residual mixed phthalate ester is then reacted in an ester-alcohol interchange step with an aliphatic polyhydric alcohol to produce methanol and the dihydropyranyl group terminated polyester. The methanol is separated from the polyester by distillation. Both ester exchange reactions are carried out in the presence of an ester exchange catalyst.

In a specific embodiment of the two step process, 3,4- dihydro-ZH-pyran 2 methyl-(3,4-dihydro-2H-pyran-2- carboxylate) and dimethyl orthophthalate in molar ratios in the range 5.17:3.35 to 2.85:5.30 are reacted in the first step in the presence of an ester-exchange catalyst, thus forming mixed methyl, dihydropyranyl esters of orthophthalic acid and methyl 3,4-dihydro-2H-pyran-2- carboxylate, the reaction mixture being maintained at a temperature in the range C. to C. and at a pressure such that the methyl 3,4-dihydro-2H-pyran-2-carboxylate separates by distillation from the other ingredicuts of the reaction mixture. In the second step, the remaining methyl ester ingredients of the reaction mixture are reacted in the presence of an ester exchange catalyst with an aliphatic polyol selected from the group consisting of ethylene glycol, polypropylene glycols and oxypropylated hexanetriols in proportions such that the methyl ester ingredients undergo an ester exchange reaction to form methanol and a mixture of polyesters containing residues of orthophthalic acid, 3,4-dihydro-2H-pyran-2- methylol and aliphatic polyol, the reaction mixture being maintained at a temperature of about 120 C. and at a pressure such that the methanol separates by distillation from the other ingredients of the reaction mixture.

Alternatively the three ingredients, dimethyl phthalate, an aliphatic polyhydric alcohol and a. vinyl ether constituted by two dihydropyranyl rings linked by a single ester linkage can react in a single step employing an ester exchange catalyst.

It has been found that the products of ester exchange reactions between dimethyl orthophthalate and (a) a dihydropyranyl compound selected from the group consisting of 3,4-dihydro-2H-pyran-2-methylol and 3,4-dihydro- 2H-pyran-2-methyl-(3,4-dihydro 2H pyran 2 carboxylate) and (b) an aliphatic polyol selected from the group consisting of ethylene glycol, polypropylene glycols and oxypropylated hexanetriols wherein the molar ratio of reactants (a) and (b) lies in the range 2.85:4.5 to 4.5205 constitute a mixture of polyesters wherein the component polyesters consist essentially of segments which are the residues of orthophthalic acid, 3,4-dihydro-2H-pyran-2- methylol and aliphatic polyols.

The proportions of ingredients may be varied to produce a polyester of desired structure provided that the resulting polyester has a large proportion of dihydropyranyl rings.

Examples of cyclic vinyl ethers suitable as ingredients for the preparation of the polyesters of this invention include 3,4-dihydro-ZH-pyran-Z-methylol (dihydropyranyl methanol) of formula H-CHz-OH ll HG 3,4-dihydro 2H pyran 2 methyl-(3,4-dihydro-2H- pyran-2-carboxylate) of formula and 3,4-dihydro-5-rnethyl 2H pyran-2-methyl-(3,4-dihydro-2H-pyran-2-carboxylate) of formula Suitable lower alkyl esters of aromatic polycarboxylic acids are dimethyl phthalate, diethyl phthalate, dimethyl terephthalate, tetramethyl pyromellitate and trimethyl trimellitate.

Aliphatic polyhydric alcohols suitable as ingredients for the preparation of polyesters of this invention include ethylene glycol, 1,5-pentanediol, glycerol, 1,2,6-hexanetriol, polypropylene glycols, castor oil, sugar alcohols, and polyether condensates of polyhydric alcohols and olefin oxides such as the polypropylene oxide condensates of hexa hydroxy sugar alcohols and propylene oxide.

Catalysts suitable for the esterification reactions of this invention include sodium metal, sodium methoxide, magnesium dihydropyranyl methoxide, tetraisopropyl titanate and sodium alkoxides of aliphatic polyhydric alcohols, such as 1,2,6-hexanetriol.

When the cyclic vinyl ether terminated polyesters of this invention are employed as ingredients in foamable compositions in admixture with a foaming agent and a catalyst, foamed cellular polymeric materials having commercially desirable properties are obtained. By choice of a suitable intermediate segment in the polyester the properties of the foamed products can be varied. For example polyesters derived from short chain dihydric alcohols, such as ethylene glycol, usually provide hard foams. When a polyhydric alcohol having a molecular weight over about 1000 is employed as ingredient in the polyester preparation flexible foams can be obtained. By similar modification of the polyester structure the viscosity of the foamable compositions can be modified. By choice of an inexpensive segment ingredient lower cost foams can be obtained.

Since the cyclic vinyl ether terminated polyesters of this invention polymerize in the presence of a catalyst to form a solid resin the polyesters also have utility as adhesives and protective coatings.

The invention will be more fully illustrated by the following examples, but it is to be understood that its scope is not to be limited to the specific embodiments shown.

EXAMPLE 1 770 grams of dimethyl phthalate (4 moles) and 900 grams (ca. 4 moles) of 3,4-dihydro-2H-pyran-2-methyl- (3,4-dihydro-2H-pyran-2-carboxylate) were placed in a two liter flask fitted with a Vigreux column 6 inches long and 1 inch in diameter and leading to a receiver, a thermoregulator, an agitator, and a side arm sealed with a rubber serum cap. The pressure in the flask was controlled by means of a manostat. The flask was heated with a heating mantle. The low boiling components of the ingredients were distilled off until the flask temperature reached 150 C. at 15 mm. mercury pressure. The distillate weighed 24.4 grams.

During a period of 1 /2 hours, while the flask tempera ture remained between 170 C. and 180 C., and pressure was 32 mm. mercury, 55 cc. of a 25% solution of sodium methoxide in methanol were added in 5 cc. portions from a syringe inserted through the rubber serum cap. During this period, 706 grams of a product comprising mainly methyl dihydropyran-2carboxylate were distilled off.

To the reaction product in the flask were added 93 grams (1 /2 moles) of ethylene glycol and the mixture Was heated at C. while gradually reducing the pressure from 160 mm. mercury to 15 mm. mercury at such rate that the ethylene glycol did not distill off. In 1% hours, the reaction was complete. During this period 30 cc. of sodium methoxide solution were added to the flask and 724 grams of dihydropyranyl polyester product were obtained, being a rather viscous liquid.

A foam was prepared from a mixture of the above product (20.0 grams) and 3,4 dihydro 2H pyran 2- methyl (3,4 dihydro 2H pyran Z-carboxylate) (20.0 grams), trichloromonofluoromethane (7.5 grams), siloxane oxyalkylene copolymer type silicone surfactant (0.2 gram) and boron trifluoride etherate/ether/trichloromonofluoromethane mixture (1 1:3 by volume) (4.0 cc.). The foam had a density of 1.82 lb./cu. ft., was somewhat friable but had a good skin and did not disintegrate after after 15 days in boiling water.

EXAMPLE 2 1 mole of dimethyl phthalate, 1.5 mole of 3,4-dihydro- 2H pyran 2 methyl (3,4 dihydro 2H pyran 2- carboxylated) and 2.0 grams of sodium metal were charged into a flask of the type employed in Example 1. The ingredients were agitated while the low boiling components (18.4 grams) distilled oflf until the temperature reached C. at 5 mm. mercury pressure. The temperature of the flask was then raised to 170 C. when a reaction took place accompanied by the distilling off of 210 grams of material in 1 hour and 10 minutes. At this time the catalyst appeared to be exhausted. 8 cc. of a 25 solution of sodium methoxide in a methanol were then added by syringe through the rubber serum cap giving an additional 65 grams of distillate.

The product remaining in the flask comprised 201 grams of liquid having a viscosity of 46 poises and 28.5 grams of a semi solid which readily settled out from the liquid.

EXAMPLE 3 A series of preparations were carried out using the apparatus and procedure described in Example 1. In the ester-ester interchange step 3,4 dihydro 2H pyran 2- methyl dihydropyran-Z-carhoxylate being distilled off. In with dimethyl phthalate in the presence of a catalyst, the methyl disydropyran-Z-carboxylate being distilled off. In the ester-alcohol interchange step a polyol was reacted with the residual product. The reactions are described in Tables I and II.

TABLE I-ESTER-ESTER INTE RCHAN GE STEP [The composition of the distillate was determined by gas liquid chromatography] ing traction distilled from 3,4-di- Residual Sodium Percent of 3,4-dihydro- 3,4-dihydrohydro-2H- 3,4-dihydromethoxide theoretical 2H-pyran-2- 2H-pyran-2- pyran-Z- 2H-pyran-2- solution Methyl (11- yield of methyl-(3,4- methyl- (3, methyl-(3, methyl-(3, Sodium in hydropymethyl di- Dimethyl dihydro-2H- 4dihydro- 4-dihydro- 4-d1hydroconsumed methanol) Total ran-2-carliydropyphthalpyran-2-ear- 2H-pyran- ZH-pyran- 2H-pyran- Dimethyl in reconsumed weight of boxylate in ran-2-carate in boxylate) in 2-caiboxyl- 2-carboxyl- 2-carboxylphthalaction, in reaction, distillate, distillate, boxylate, distillate, distillate, ate), moles ate), moles ate), moles ate, moles grams cc. grams moles percent 1 moles moles A 2.00 0. 07 1. 93 2. 00 3. 59 264 1. 68 88 0. 10 0. 016 B-.- 2. 00 0. 07 1. 93 2. 00 2. 08 9. 0 304 1. 68 93 0. 225 0. 12 C--. 6. 00 0. 18 6. 82 4.00 1. 12 34. 2 863 4. 10 79 0. 65 0. 65 D--- 4. 5O 0. 17 4. 33 4. 50 1. 28 24. O 660 3. 81 0. 68 0. 11 E..- 3. 00 0. 14 2. 86 6. 00 1. 20 28. 3 461 2. 22 78 0. 70 0. 01

1 The yield of methyl dihydrfip'yran-2-carboxylate is shown as a percentage of 3,4-dihydro2H-pyran-2-methyl-(3,4-dihydro-2H-pyran-2-carboxylate) residual, less amount in the dist e.

TABLE II-ESTE R-ALC OHOL INTE RCHAN GE STEP Reaction time (ester-ester Dihydro- Percent interchange Sodium pyranyl W./W. of and ester- Amount metlioxide Methanol methanol Weight semi-solids Viscosity alcohol of polyol, consumed, recovered, recovered, of product, in product, of product, interchange),

Polyol moles cc. moles moles grams percent poises hours A LET 112 g} 9. 0 1.88 o. 41 1, 410 5. 0 4e 1 B 0. 66 11. 0 1. 90 0.41 1, 677 54 1% C 0. 6 6. 8 1. 0 0. 32 1,144 4. 4 13 2 D 2. 0 10. 0 3. 4 1,125 6. 8 148 2 4. 5 8. 2 7.0 0. 41 1, 301 5. 2 98 2 PP G1025=Polypropylene glycol of 1,025 molecular weight and average hydroxyl number (mg. KOH/gm.) 110. LH167=Oxypropylated hexanetriol of 2,500 molecular Weight and average hydroxyl number (mg. KOH/gm.) 67. LHT-112= Oxypropylated hexanetriol of 1,500 molecular Weight and average hydroxyl number (mg. KOH/gm.) 112.

Catalyst: aqueous fluoboric acid by weight) or boron etherate dissolved in ethyl ether and trichloromonofluoromethane in proportion of 1:1:3 parts by volume and optionally 3,4-dihydro-ZH-pyran-Z-methyl (3,4-dihydro-ZH-pyran 2 carboxylate) methyl dihydropyran- Z-carboxylate.

The compositions were mixed vigorously in 250 cc. plastic cups. The compositions and resulting foams are shown in Table III, the source of the dihydropyranyl polyester ingredient being shown by reference to Table I and H.

EXAMPLE 4 291 grams (1.5 moles) of dimethyl phthalate, 1250 grams (0.5 mole) of polypropylene glycol of molecular Weight 2500 and 1008 grams (4.5 moles) of 3,4-dihydro- ZH-pyran-Z-methyl-(3,4-dihydro-2H-pyran 2 carboxylate) were charged into the reaction vessel of the type described in Example 1. The pressure was reduced to 6 mm. of mercury and the reaction mixture was heated until the temperature reached 140 C. During this time 10.0 grams of material distilled off. I

3.84 grams of sodium metal and 2 cc. of 25% solution of sodium methoxide in methanol were added to the reaction mixture. The reaction mixture was stirred vigorously and heated at 140-150 C. while the pressure in the vessel was reduced slowly from to- 3 mm. of mercury at such a rate that the 3,4-dihydro-2I-I-pyran-2-methyl- (3,4-dihydro-2H-pyran-2-carboxylate) did not distill over. The distillate contained 1.16 moles of methyl dihydropyran-Z-carboxylate, 0.54 mole of dihydropyranyl methanol, 0.024 mole of 3,4-dihydro-2H-pyran-2-carboxaldehyde and 1.32 moles of methanol.

TABLE III 3,4dihydro-2H- Amount of pyran-2-methyl- Methyl dihydro- (3,4-dihydro-2H- dihydro- Amount Tcmpera- Cure time pyranyl pyran-Z-carpyran-2- of Induction Rise ture at (minutes)/ polyester, boxylate), carboxylate, catalyst, time, time, start of temperature grams grams grams Catalyst cc. minutes minutes rise, 0. 0 Comment 1.0 1 5/130 28 3.0 1% 2% 42 20/75 Flexible. 30 3. 0 1% 2 44 10/25 Do. 30 1.0 1% 1% 46 Do. 30 0. 1% 2% 52 30/80 Soit, flexible. 40 0. 2 2% 3% 36 20/80 30 0.6 V 960/ Haralio 0. 7 2 2 4 2 FB 0.5 1% 33 30/80 Soft.

FB=Aqueous fiuoboric acid (50% by Wei ht B13 =Boron trifiuori The reaction product remaining in the reaction vessel Was a liquid with viscosity of 22 poises.

The aforesaid reaction product was mixed with trichloromonofiuoromethane foaming agent and boron trifluoride etherate catalyst to give flexible foams having 8 ble with fine cell structure. When the products of EX- amples and 6 were blended and employed in analogous foaming'compositions the foams obtained were more resilient than when the product ofExample 6 was employed alone.

good tear strength and high resiliency. These foams were 5 EXAMPLE 7 equivalent to those prepared from dihydropyranyl poly- 582 grams of dimethyl phthalate 637 grams of p01? esters made by the two Stage process propylene glycol of molecular weight 425, 513 grams of EXAMPLE 5 I dihydropyranyl methanol and cc. of 25% commercial moles of dimethyl phthalate, 05 mole of Poly 0 sodium methoxide solution in methanol wereheated to propylene glycol of, molecular weight 2500 and 4.5 mole 120 at f mercury pressllfe m flask adapged of 3, 4 dihy drO 2'H pyran 2 methy1 (3,4 dihydro for vacuum distillation and for addition of catalyst un er pyranawarboxylatel were chargfid into a reaction vessel vacuum. Dur ng a perlod of 3 hours, while addit onal so- Of type described in Example The pressure of the 1 drum methoxlde solution was added atmte rvals in 10 cc. vess 61 was reduced to 3 mm mercury and the reaction portions and 183.3 grams of methanol distilled over into mixture heated to distill off the low boiling components, the Cold traps, the pressure In the flask was gradu'flny the temperature rising to grams of Sodium duced to 3 mm. mercury. At the end of the reaction the metal were then added to the reaction mixture but no flask temperature was ralsed to 150 and P methanol distilled over. However, when 7 cc. of. 25% acted dlhydropyranyl methanol (153 grams) was dlstlued solution of sodium methoxide in methanol were added a Ofi I reaction commenced. Once initiated the reaction proceeded. h F Q P F remalnlrlg In the k dark smoothly giving in 45 minutes at 0 L l f liquid having a viscosity of 63 polses at room temperature. methanol, 0.35 mole of methyl dihydropyran-Z-carboxylof four foams Was Prepared emP1 Ymg as ate and 018 mole of dihydropyranyl methanol. 25 gredlents in each foam, 40 grams of the reactlon product. The temperature of the reaction mixture was then raised 5 tnchlommonofluorn}thane 02 slloxane to 140150 C. An additional 8 cc. of sodium methoxide alkylene copolymer type slhcme surfastant and as solution were then added and in 1 hour 1.10 mole of a1Yst 5 of a by Volume sohmon of boron methyl dihydropyran-2-carboxylate and 0.55 mole of diflufmde etherate YP PY mfifleculaf hydropyranyl methanol distilled oven 30, weight 425. In two foams an additional ingredient d1- The dihydropyranyl polyester product remaining in the hydropyran'z'carboxyl'lc acld n'butyl ester was employed reaction vessel was a liquid of viscosity of 40 poises f fi ShOWP In Table weighing 2060 grams. When employed as ingredient of a The ingredients wlth the exception of the catalyst were foaming composition containing trichloromonofl'uoroblended TaPldlY for SecPndS In a 250 1111- Paper P- methane and boron trifluoride etherate soft flexible foams The tempemtufe 0f the m Was o d and 5 Were obtained. of the catalyst were added in a single portion and blended EXAMPLE 6 1n the mixture for 15 seconds. The temperature was then measured and the mixture was set aside to foam. When 2.5 moles of dimethyl phthalate, 5 moles of 3,4-difoaming commenced the temperature was recorded again. hydro-2H-pyran-2-methyl-(3,4-dihydro 2H pyran 2- The characteristics of foaming are shown in Table IV.

TABLE IV Temperature of composition Dihydropyran- Period of Before After At be- Z-carboxylic Induction Rise cure at Height adding adding ginning of acid n-butyl period, period, 100 (2., of ioarn, catalyst, catalyst, loam rise, 1' oaln ester, grams mm. mm. mm. in. C. C. C

o 1% 1 2s 31 37 0 1 1 2s 33 36 5 2 so 7% 2s 2s 33 10 2% 20 6% 25 27 '30 carboxylate) and 0.83 mole of polypropylene glycol of The foams when freshly prepared had tacky skins but molecular weight 2500 were charged into a reaction vesthe skins became satisfactory after curing in an oven at sel of the type used in Example 1. The low boiling com- 100 C. Foam A collapsed on standing which suggests ponents of the reaction mixture were first distilled off that curing improves the mechanical strength of the prodand then 2.14 grams of sodium metal were added. The 60 uct. All the four foams were soft and flexible and were reaction was carried out in two stages as in Example 5, characterized by rather slow recovery from deformathe total reaction time being about 2 hours. During the tion. Foam D, prepared from a dihydropyranyl polyreaction 19 cc. of sodium methoxide solution (25% in ester and dihydropyran-Z-carboxylic acid n-butyl ester, methanol) were added to the reaction mixture, while Changed shape only slightly after remaining 4 days in there were distilled over 2.44 moles of methyl dihydro boiling water. In distinction, foams prepared from the pyran-Z-carboxylate, 1.2 mole of dihydropyranyl methd e st r f polypropylene glycol (MW 425) and dihyanol and 2.0 moles of methanol (allowance being made QPYI I-Z-CaIbOXyIic acid disintegrated under such test for the methanol content of the catalyst solution). C nditi ns.

The product in the reaction vessel comprised 2131 WhatIClaimisI grams of liquid having a viscosity of 81 poises and 53 A miXillre f p lyesters wherein the component grams of a semi solid which readily settled out from polyesters consist essentially f segments which r h the liquid. residues of orthophthalic acid, 3,4-dihydr0-2H-py -an-2- The liquid was employed as an ingredient in foaming I Y a aliphatic P Y Said polyesters mp compositions including trichloromonofiuoromethane and g the pro c f st ang r acti ns between diboron trifiuoride etherate. The foams resulting were fleximethyl orthophthalate and (a) a dihydropyranyl compound selected from the group consisting of 3,4-dihydro- 2H-pyran-2-methylol and 3,4-dihydro-2H-pyran-Z-methyl- (3,4-dihydro-2H-pyran-2-carboxylate), and (b) an aliphatic polyol selected from the group consisting of ethylene glycol, polypropylene glycols and oxypropylated hexanetriols, provided that the molar ratio of reactants (a) and (b) lies in the range of 2.85:4.5 to 4.5205.

2. A process for preparing mixtures of dihydropyranyl group-containing polyesters which comprises (1) reacting 3,4-dihydro-2H-pyran-2-methyl-(3,4-dihydro-2H pyran- 2-carboxylate) and dimethyl orthophthalate in molar ratios in the range 5.17:3.35 to 2.85:5.30 in the presence of an ester exchange catalyst, thus forming mixed methyl, dihydropyranyl esters of orthophthalic acid and methyl 3,4-dihydro-2H-pyran-2-carboxylate, the reaction mixture being maintained at a temperature in the range 170 C. to 180 C. and at a pressure such that the methyl 3,4-dihydro-ZH-pyranQ-carboxylate separates by distillation from the other ingredients of the reaction mixture, and (2) reacting the remaining methyl ester ingredients of the reaction mixture in the presence of an ester exchange catalyst With an aliphatic polyol selected from the group consisting of ethylene glycol, polypropylene glycols and oxypropylated hexanetriols, in proportions such that the methyl References Cited UNITED STATES PATENTS 3,032,558 5/1962 Montagna et al. 260345.8 3,158,585 11/1964 Kelso et al 260-345.8 3,197,320 7/1965 Graham et al. 260345.8 3,206,479 9/1965 Sax 260345.8 3,318,824 5/1967 Graham 260-3458 NORMA S. MILESTONE, Primary Examiner US. Cl. X.R. 26075, 2.5 

